Airway resistance

Question 1

what is airways resistance?

Answer 1

the opposition to flow caused by the force of friction

Question 2

how is airways resistance defined?

Answer 2

it is defined as the ration of driving pressure to the rate of air flow

Question 3

name three things that resistance to flow is dependent on

Answer 3

whether the flow is laminar or turbulent, on the dimension of the airways and on the viscosity of the gas

Question 4

describe the resistance in laminar flow and how does this affect the pressure required to produce a certain flow rate?

Answer 4

resistance is quite low and so a relatively small driving pressure is needed to produce a certain flow rate

Question 5

describe the resistance in turbulent flow

Answer 5

resistance is relatively large compared to laminar flow and so a much larger driving pressure would be required to produce the same flow rate

Question 6

describe airflow in the small bronchi, bronchioles, respiratory bronchi and alveoli and therefore air resistance here

Answer 6

airflow is laminar and therefore there is less resistance to airflow

Question 7

describe the airflow in the larger airways i.e. oral and nasal cavity, trachea and bronchi and therefore air resistance here

Answer 7

airflow is turbulent and therefore resistance to airflow is greater

Question 8

what happens to airflow in the trachea and bronchi during exercise and why?

Answer 8

it becomes more turbulent as you begin ventilating more heavily

Question 9

what creates turbulence in the airways?

Answer 9

cartilage

Question 10

in quite breathing, describe the airflow in the trachea and bronchi?

Answer 10

transitional flow - a mixture of laminar and turbulent flow. it is laminar through most of the airway and then turbulent as the airway bifurcates.

Question 11

describe the effects of the sympathetic and parasympathetic nervous system on the nose

Answer 11

SNS increases vasoconstriction (which reduces airway resistance) and decreases secretion.
PNS causes mucosal swelling and increases nasal mucus secretion

Question 12

what is the pharynx?

Answer 12

a collapsible tube behind the nose and mouth that connects them to the oesophagus

Question 13

what do the muscles of the pharynx do during inspiration

Answer 13

during inspiration the muscles of the pharynx wall hold airways open and are synchronous with the diaphragm

Question 14

how is the pharynx important in swallowing?

Answer 14

it senses a bolus of food and triggers a response that shuts down respiration, closes the glottis and raises the larynx, to prevent food from getting into the airways, diverting food to the oesophagus

Question 15

what two things is the larynx important for

Answer 15

1. phonation - the process by which folds of the vocal cords produce sound
2. protects lower airways from alimentary/digestive tract contents (either from reflux or swallowing)

Question 16

what is the epiglottis?

Answer 16

a fibrous, cartilage that overhangs laryngeal inlet

Question 17

what is the function of the epiglottis?

Answer 17

helps slide food into the oesophagus during swallowing and preventing food from entering the lungs

Question 18

what is very important in the swallowing process?

Answer 18

closure of the glottis (space between vocal cords)

Question 19

what receptor is found on the posterior wall of the trachea and what are they involved in?

Answer 19

slowly adapting stretch receptors, that sense air flow through the trachea and the pressure excerpted on the wall and feedback to the respiratory control centre to help modulate rate and depth of breathing

Question 20

name the second type of receptor found in the trachea and what is their function?

Answer 20

rapidly adapting receptors may be stimulated by an irritant and cause a cough reflex - bronchoconstriction and mucus production through parasympathetic pathway

Question 21

what affect does the parasympathetic nervous system have on the lungs and how?

Answer 21

causes bronchoconstriction, through the release of acetylcholine binding muscarinic receptors

Question 22

at rest, our airways are always under some degree of …. tone, this nerve is a component of the …. nervous system and results in ….

Answer 22

vagal
parasympathetic
bronchoconstriction

Question 23

which supply (the parasympathetic/sympathetic) supply is activated in the cough reflex and why?

Answer 23

the parasympathetic supply to cause bronchoconstriction, so that you can push a large volume of air out the lungs through narrow airways and generate a lot of force to push out the content of the lungs

Question 24

what is the difference between epinephrine and norepinephrine?

Answer 24

norepinephrine is the main neurotransmitter of the SNS and epinephrine is the main hormone secreted by the adrenal medulla.

Question 25

what causes bronchodilation of the airways and what sort of response is this?

Answer 25

epinephrine binding B2-adrenergic receptors, this is a sympathetic response.

Question 26

why does norepinephrine rarely act on the airways and what affect would it have?

Answer 26

there is little to no sympathetic nerve innervation to the airways, but this would cause bronchodilation much like epinephrine

Question 27

during exercise what sort of response do you want to have in you airways and why?

Answer 27

a sympathetic response, to get more air into the lungs and get rid of CO2

Question 28

along with sympathetic and parasympathetic responses in the airways, name the third type of response and give two examples with the effect that they have

Answer 28

petinergic response substance P binds neurokinin receptors and causes bronchoconstriction and vasoactive intestinal polypeptide (VIP) binds VIP receptors and causes bronchodilation

Question 29

what do beta agonists mimic and what affect do they have?

Answer 29

they mimic epinephrine and cause bronchodilation, this decreases resistance and makes it easier to breathe

Question 30

name two ways that you can reduce the radius of the airways and what does this lead to?

Answer 30

smooth muscle contraction and increased bronchial secretions this leads to increase resistance in the airways

Question 31

where and how is mucus produce?

Answer 31

goblet cells produce mucins which are hydrated to produce mucus

Question 32

in airways, the activation of which pathway increases mucus secretion? and what is this usually in response to?

Answer 32

cholinergic (parasympathetic) pathway | this is usually in response to irritants e.g. cigarette smoke

Question 33

the sympathetic supply has little effect on bronchial secretion, give two examples of when it does

Answer 33

a1-adrenegruc receptor inhibit secretion | b2-adrenerguc receptors will stimulate secretion

Question 34

increased production of mucus as a response to cigarette smoke is a protective response, why are these people more likely to get infections?

Answer 34

factors in cigarette smoke the decrease cilia motility and so you get less clearance of mucus